The present invention relates to a cleaning device for cleaning a printhead of an ink-jet printer that carries out printing by ejecting ink droplets onto a recording medium.
The ink-jet printer ejects ink droplets onto a recording medium from a plurality of nozzles formed on an ink ejecting surface of a printhead by applying instantaneous pressure to the ink within the nozzles. The instantaneous pressure is generated, for example, by elements that convert electrical energy into mechanical energy, such as a piezoelectric element, or elements that convert electrical energy into heat.
The ink-jet printer prints characters and images by ejecting ink droplets onto the recording medium and thereby forming a plurality of small dots thereon. A great advantage of such an ink-jet printer is that it can provide a high quality color image printer of a relatively simple structure by ejecting different color inks from different nozzles of the printhead. However, it should be noted there are also some problems typical to ink-jet printers.
One of such typical problems is that the ink adheres to the ink ejecting surface or nozzles of the printhead during the printing operation.
The ink adheres to the ink ejecting surface or nozzles when bubbles are generated in the ink within or near the nozzles due to temperature increase within the printer as a result of a long, continuous use thereof. These bubbles not only hinder the ink droplets ejected from the nozzles to fly toward the recording medium along expected trajectories, which causes deterioration of printing quality, but also atomize the ejected ink. The atomized ink suspends in the vicinity of the ink ejecting surface, instead of flying toward the recording medium, and a part of them adheres to the ink ejecting surface or nozzles.
The adherence of ink to the ink ejecting surface or nozzles may occur even if the bubble mentioned above are not generated. For example, some of the ejected ink droplet bounces back from the recording medium and adheres to the ink ejecting surface.
If the printer is not used for a long time with the adhered ink left on the ink ejecting surface or at the nozzle opening, the nozzle will be clogged with dried ink. Once the nozzle is clogged, the print quality begins to fade or it becomes unprintable since the amount of ejected ink decreases or no ink can be ejected.
The clogging of the nozzle with dried ink cannot be removed by merely applying pressure to the ink with the piezoelectric element or heating element mentioned above. Therefore, various methods for preventing or removing the clogging of the nozzle are provided.
Typical methods for preventing or removing clogging of the nozzle includes capping, wiping, ink suction, and preparative ink discharge (or flushing).
In capping, the ink ejecting surface of the printhead is tightly covered with a rubber cap member to prevent drying of the ink. The cap member covers the ink ejecting surface, for example, when the ink-jet printer is not in use for a long time, or, over the interim time period between one printing cycle and another.
In wiping, the ink ejecting surface of the printhead is rubbed with a blade like member at a predetermined timing or predetermined interval to wipe the ink ejecting surface clean.
In ink suction, the ink is removed from the nozzle under suction at a predetermined interval, timing, of step. In preparative ink discharge or flushing, minute dust or paper and/or fiber, for example, and small ink clots are removed from the nozzles by flushing ink from the nozzles.
It should be noted that one or a combination of the above-mentioned methods are typically used in the ink-jet printer to prevent the clogging of the nozzles of the printhead.
If wiping is carried out, the blade should be cleaned to remove the ink adhered thereto. Otherwise, the wiping becomes ineffective or ink remaining thereon drops down and makes the printer dirty. Typically, the ink remaining on the blade is removed by bringing the blade into contact with an ink absorber, or by utilizing the springing back of the blade after being bent.
Devices that prevent or remove clogging of the nozzle by practicing the above-mentioned methods are called cleaning devices or recovering devices. Such cleaning (recovering) devices are essential for the ink-jet printer to maintain high quality printing.
Japanese Patent Publication No. 2726076 discloses an ink-jet printer in which ink ejecting surfaces of printheads held in a carriage are wiped with a cleaning blade in the following manner. First, the printheads are moved out of a printing area of the printer. Then, the cleaning blade is abutted against the ink ejecting surface of the first printhead and moved along the ink ejecting surfaces in a direction along which the printheads are arranged. After having wiped off the ink ejecting surfaces, the cleaning blade is moved for a while with the tip portion thereof being rubbed against an ink absorber located behind the recording medium, and then the cleaning blade is stopped. Next, the printhead is returned to the printing area so as to avoid coming into contact again with the cleaning blade, and then the cleaning blade is moved back to the initial portion thereof.
The ink-jet printer disclosed in the above-mentioned Japanese Patent Publication, however, requires much time for the cleaning operation since the printhead is once moved out of the printing area, for allowing wiping of the ink ejecting surface with the cleaning blade, and then moved back to the printing area for allowing the cleaning blade returning to the initial position without coming into contact with the printhead.
Japanese Patent Application Provisional Publication HEI 11-138857 discloses an ink-jet printer in which a cleaning blade wipes off an ink ejecting surface of a printhead, and then moves toward an ink absorber so as to remove the ink adhered to the tip portion thereof by rubbing the tip portion against the ink absorber. The cleaning blade is bent by the ink absorber, springs back as it leaves the ink absorber and thereby scatters or removes the ink adhered to cleaning blade at portions other than the tip portion. The cleaning blade is placed in a blade holder that is coupled to a disk via a link mechanism. The disk rotates to move the blade holder, and hence the cleaning blade, up and down. After the ink adhered to the cleaning blade is removed, the cleaning blade is moved down by rotating the disk so that the cleaning blade does not come into contact with the ink ejecting surface.
Since the printer disclosed in the above mentioned publication lifts the cleaning blade up when the ink ejecting surface of the printhead is to be wiped, and moves down the cleaning blade when the cleaning blade is to be returned to the initial position, the printer requires a complicated mechanism that utilizes a rotating disk to move up and down the blade holder and also an additional motor for driving the disk.
The ink removed from the cleaning blade by the ink absorber, or the ink discharged into a cap member under suction or by flushing are typically dealt with as below.
In printers for consumer use, which are not frequently used and of which ink consuming amount is small, the ink discharged from the printhead into the cap member is absorbed by an ink absorber and then dried by air seasoning. Further, the ink adhered to the cleaning blade during the wiping operation is removed by abutting the cleaning blade against other members or dried by air seasoning.
In printers for commercial use, which are frequently used and of which ink consuming amount is large, it is required to deal with the waste ink more actively.
For example, in the printer disclosed in Japanese Patent Application Provisional Publication No. P2000-43280, an ink absorber is attached to a cleaning blade to integrally move therewith during the wiping operation. A tube is connected to the ink absorber to remove the ink within the ink absorber by suction.
In the printer disclosed in Japanese Patent Application Provisional Publication No. P2001-30508, a cleaning blade abuts against an ink absorber after the wiping operation to remove the ink remaining on the cleaning blade. The ink absorbed into the ink absorber is collected into a collecting space provided within a cap member, which caps the printhead during a purging operation, and then sucked out from the collecting space by a pump.
In the printers disclosed in the Japanese Patent Application Provisional Publications Nos. P2000-43280 and P2001-30508, however, the waste ink cannot be removed effectively since the ink is removed, by suction, after once introduced into the ink absorber attached to the cleaning blade or the ink collecting space provided within the cap member. Thus, the disposal of the waste ink cannot be carried out in sufficient speed if a recording medium of a very large size is to be printed or if a large amount of recording medium is to be printed.
Therefore, there is a need for a cleaning device that is capable of cleaning a printhead of an ink-jet printer while effectively discarding the waste ink collected during the cleaning operation.
There is also a need for a cleaning device that is capable of cleaning a printhead of an ink-jet printer with a simple structure and in a relatively short operation time.